NAME

gethostbyname, gethostbyaddr, gethostent, sethostent, endhostent − get network host entry

SYNOPSIS

#include <netdb.h>

extern int h_errno;

struct hostent ∗gethostbyname(name)
char ∗name;

struct hostent ∗gethostbyaddr(addr, len, type)
char ∗addr; int len, type;

struct hostent ∗gethostent()

sethostent(stayopen)
int stayopen;

endhostent()

DESCRIPTION

Gethostbyname and gethostbyaddr each return a pointer to an object with the following structure.  This structure contains either the information obtained from a name server, such as netinfod(8), named(8), or ypserv(8) or broken-out fields from a line in /etc/hosts. 
 
If NetInfo is not running these routines do a lookup in /etc/hosts.

structhostent {
char∗h_name;/∗ official name of host ∗/
char∗∗h_aliases;/∗ alias list ∗/
inth_addrtype;/∗ host address type ∗/
inth_length;/∗ length of address ∗/
char∗∗h_addr_list;/∗ list of addresses from name server ∗/
};
#defineh_addr  h_addr_list[0]/∗ address, for backward compatibility ∗/

The members of this structure are:

h_name Official name of the host. 

h_aliases A zero terminated array of alternate names for the host. 

h_addrtype The type of address being returned; currently always AF_INET. 

h_length The length, in bytes, of the address. 

h_addr_list A zero terminated array of network addresses for the host.  Host addresses are returned in network byte order. 

h_addr The first address in h_addr_list; this is for backward compatiblity. 

DIAGNOSTICS

Error return status from gethostbyname and gethostbyaddr is indicated by return of a null pointer.  The external integer h_errno may then be checked to see whether this is a temporary failure or an invalid or unknown host. 

h_errno can have the following values:

HOST_NOT_FOUNDNo such host is known. 

TRY_AGAINThis is usually a temporary error and means that the local server did not receive a response from an authoritative server.  A retry at some later time may succeed. 

NO_RECOVERYThis is a non-recoverable error. 

NO_ADDRESSThe requested name is valid but does not have an IP address; this is not a temporary error.  This means another type of request to the name server will result in an answer. 

FILES

/etc/hosts - if NetInfo is not running

SEE ALSO

hosts(5), resolver(3), named(8), netinfo(5)

BUGS

All information is contained in a static area so it must be copied if it is to be saved.  Only the Internet address format is currently understood. 

4.2 Berkeley Distribution  —  May 20, 1986